1. Field of the Invention
The present invention relates to a method of installing thermal insulation, and more particularly, to a method and device for quickly fastening and unfastening a thermal blanket to the skin of a spacecraft.
2. Background Information
Reusable space launch vehicles, such as the space shuttle, are exposed to extreme cold and extreme heat. For example, in contrast to the subzero temperatures encountered in space, a space launch vehicle may be exposed during reentry to hull temperatures exceeding 1,800.degree. F. Some form of thermal insulation is required to protect the space launch vehicle from these extremes in temperature. Currently, the space vehicles use ceramic tiles as protection. However, it has been suggested that as an alternative, flexible quilted ceramic blankets 20, as shown in FIG. 1, could be used to cover the exteriors of such space vehicles for protection.
The proposed flexible blankets 20, shown in FIG. 1, are constructed of a fiber batting 22. The batting 22 is surrounded by a cover material 24, and quilted with ceramic thread 26 to form the blanket 20.
The blankets 20 are mounted onto a hull exterior 29 of the space vehicle 28 with a silicon rubber adhesive 30, as shown in FIG. 2. Unfortunately, the blankets 20 when adhered to a structure using the silicon rubber adhesive 30, often do not withstand high acoustic loads to which the space vehicle 28 are subjected during reentry. Acoustical loads of this magnitude often cause the quilting threads to break, and the batting to separate and puff up. This reduces the performance of the insulating blanket to unacceptable levels. Another disadvantage of mounting the blankets 20 with the silicon adhesive 30 is that the adhesive 30 becomes brittle over areas having very low temperatures, such as over cryotanks.
Yet another disadvantage of mounting the blankets 20 onto the space vehicle 28 using the silicon rubber adhesive 30, as shown in FIG. 2, is that the blankets 20 must often be removed and replaced for inspection, repair, or to obtain access to various hatches. The current process for removing the blankets 20 requires the blankets 20 to be literally scraped off the hull 29 of the launch vehicle 28. The removal process is both time consuming and expensive. Since turnaround time for reusable launch vehicles is increasingly critical to their success, the extensive time required for the removal and replacement of insulation blankets mounted with adhesive is unacceptable.
Attempts to replace the silicon rubber adhesive 30 with a mechanical device have so far failed because the mechanical devices have failed to prevent the blankets 20 from sagging in the areas where the blankets were not mechanically fastened to the vehicle hull 29. When attempts to mechanically fasten the blankets 20 to the hull 29 were attempted, the mechanical fastener was exposed on the exterior of the blanket to enable the use of tooling to remove and install the blanket 20 onto the hull 29 of the vehicle 28. Unfortunately, testing showed that these exposed areas act as heat sinks, which draw the heat of reentry into the hull causing hull failure. Further, any attempts to attach the mechanical devices to the hull 29 would be difficult to remove once drilled or welded to the exterior of the hull 29.
Accordingly, there is a need in the art for a means of quickly installing and removing the flexible blankets 20 from the hull 29 of the space vehicle 28. Further, any means for holding the blankets in position must prevent sagging, and be reliable even when exposed to intense vibration and heat, typically encountered during a space vehicle's reentry into the earth's atmosphere.